Applications, appeals, permitted development, enforcement and planning strategy across England
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Class A windows and doors: alterations to your house
Class A covers improvements and other alterations to a qualifying house as well as extensions. This guide focuses on windows, doors, external materials and garage-conversion alterations in England.
For enlargement measurements, use the complete Class A extension guide. An alteration and an extension can form one project, so every relevant part must comply.
Need help with permitted development?
Permitted development can avoid a full planning application, but only if the right applies and every relevant limit and condition is met. Planning Geek can check the planning history, Article 4 directions and other restrictions, and help with a lawful development certificate or prior approval where needed.
Replacing or adding windows and doors
Class A can cover new or altered openings and replacement windows and doors, subject to the applicable limits and conditions. Some like-for-like work may not be development at all; where planning permission is required, establish whether the Class A right applies.
Materials used in exterior work must have a similar appearance to the exterior of the existing house, apart from the statutory exception for materials used in constructing a conservatory. A different product is not automatically a different appearance, but substantial changes of finish and design need assessment.
Check the actual scope of any planning condition or Article 4 direction. A direction affecting windows can matter even when no extension is being built. Listed building consent is separate and may be required for changes affecting a listed building’s special character.
Upper-floor side windows: both conditions apply
Any upper-floor window in a wall or roof slope forming a side elevation must be:
- Obscure-glazed
- Non-opening, unless every part which can open is more than 1.7 m above the floor of the room
The illustration above shows the two requirements together. Exactly 1.7 m is not enough for an opening part. A high opening still needs obscure glazing. Measure from the internal floor rather than the ground outside.
A.3(b) specifically concerns upper-floor side windows. It does not create the same blanket condition for every ground-floor window, although other applicable conditions and restrictions may matter.
Identify all side elevations, including those of projecting wings or outriggers. A window does not become rear-facing simply because it is located behind the main block of the house.
Bay windows and projecting alterations
A new bay window can enlarge the house. Class A does not permit an enlargement beyond a wall forming the original principal elevation, even where that elevation does not front a highway. An enlargement beyond an original highway-fronting side wall is also excluded.
Assess projecting work under the relevant enlargement rules, not simply as a replacement window. A new entrance extension may need the separate Class D porch tests.
Cladding on protected land
On article 2(3) land, Class A excludes cladding any part of the exterior with stone, artificial stone, pebble dash, render, timber, plastic or tiles.
This is additional to the protected-land restrictions on side and multi-storey rear enlargements. Do not assume matching the old appearance removes the specific cladding restriction.
Garage conversion alterations
Replacing a garage door with a wall and window may be an alteration to the house, but check whether a planning condition requires the garage to remain available for parking. The GPDO does not override a contrary planning condition.
Creating a separate dwelling is a different proposal. Read the garage conversion guide and establish the lawful position for both the building work and proposed use.
Which houses can use Class A?
- The right is for a dwellinghouse, not a flat, maisonette or building containing flats
- It is unavailable where permission to use the house as a house arose only through Part 3 Classes G, M, MA, N, P, PA or Q
- A dwellinghouse built under Part 20 is excluded
- Relevant planning conditions and Article 4 directions can remove the right
The existing building and use must be lawful. Class A’s highest-roof and eaves limits apply to the part enlarged, improved or altered. If the work also enlarges the house, use the main checklist for ground coverage, original-wall projections, joined enlargements, height, storeys and roof pitch.
Work covered by a different class
Class A excludes alterations to any part of the house’s roof; assess Class B and Class C as relevant. It also excludes the specified chimney, flue, soil and vent pipe and microwave-antenna works, and the provision of a verandah, balcony or raised platform.
Class A’s upper-floor roof-window condition does not itself grant permission for the roof alteration. Combined work can need more than one class.
Before starting
Ordinary qualifying Class A alterations have no prior approval procedure. A certificate of lawfulness for proposed development can establish whether your proposal is lawful. Building Regulations, structural requirements and private rights remain separate.
Sources and Class A legislation
Checked against the current GPDO Part 1 and article 2 definitions. The government householder technical guidance provides explanations and examples, but must be read with subsequent amendments to the legislation.
Read the Class A legislation
Class A – enlargement, improvement or other alteration of a dwellinghouse
Permitted Development
A. The enlargement, improvement or other alteration of a dwellinghouse.
Development not permitted
A.1 Development is not permitted by Class A if—
(a)permission to use the dwellinghouse as a dwellinghouse has been granted only by virtue of Class G, M, MA, N, P , PA or Q of Part 3 of this Schedule (changes of use);
(b)as a result of the works, the total area of ground covered by buildings within the curtilage of the dwellinghouse (other than the original dwellinghouse) would exceed 50% of the total area of the curtilage (excluding the ground area of the original dwellinghouse);
(c)the height of the part of the dwellinghouse enlarged, improved or altered would exceed the height of the highest part of the roof of the existing dwellinghouse;
(d)the height of the eaves of the part of the dwellinghouse enlarged, improved or altered would exceed the height of the eaves of the existing dwellinghouse;
(e)the enlarged part of the dwellinghouse would extend beyond a wall which—
(i)forms the principal elevation of the original dwellinghouse; or
(ii)fronts a highway and forms a side elevation of the original dwellinghouse;
(f)subject to paragraph (g), the enlarged part of the dwellinghouse would have a single storey and—
(i)extend beyond the rear wall of the original dwellinghouse by more than 4 metres in the case of a detached dwellinghouse, or 3 metres in the case of any other dwellinghouse, or
(ii)exceed 4 metres in height;
(g)for a dwellinghouse not on article 2(3) land nor on a site of special scientific interest, the enlarged part of the dwellinghouse would have a single storey and—
(i)extend beyond the rear wall of the original dwellinghouse by more than 8 metres in the case of a detached dwellinghouse, or 6 metres in the case of any other dwellinghouse, or
(ii)exceed 4 metres in height;
(h)the enlarged part of the dwellinghouse would have more than a single storey and—
(i)extend beyond the rear wall of the original dwellinghouse by more than 3 metres, or
(ii)be within 7 metres of any boundary of the curtilage of the dwellinghouse being enlarged which is opposite the rear wall of that dwellinghouse;
(i)the enlarged part of the dwellinghouse would be within 2 metres of the boundary of the curtilage of the dwellinghouse, and the height of the eaves of the enlarged part would exceed 3 metres;
(j)the enlarged part of the dwellinghouse would extend beyond a wall forming a side elevation of the original dwellinghouse, and would—
(i)exceed 4 metres in height,
(ii)have more than a single storey, or
(iii)have a width greater than half the width of the original dwellinghouse;
(ja)any total enlargement (being the enlarged part together with any existing enlargement of the original dwellinghouse to which it will be joined) exceeds or would exceed the limits set out in sub-paragraphs (e) to (j);
(k)it would consist of or include—
(i)the construction or provision of a verandah, balcony or raised platform,
(ii)the installation, alteration or replacement of a microwave antenna,
(iii)the installation, alteration or replacement of a chimney, flue or soil and vent pipe, or
(iv)an alteration to any part of the roof of the dwellinghouse ; or
(l)the dwellinghouse is built under Part 20 of this Schedule (construction of new dwellinghouses).
A.2 In the case of a dwellinghouse on article 2(3) land, development is not permitted by Class A if—
(a)it would consist of or include the cladding of any part of the exterior of the dwellinghouse with stone, artificial stone, pebble dash, render, timber, plastic or tiles;
(b)the enlarged part of the dwellinghouse would extend beyond a wall forming a side elevation of the original dwellinghouse; or
(c)the enlarged part of the dwellinghouse would have more than a single storey and extend beyond the rear wall of the original dwellinghouse;
(d)any total enlargement (being the enlarged part together with any existing enlargement of the original dwellinghouse to which it will be joined) exceeds or would exceed the limits set out in sub-paragraphs (b) and (c).
Conditions
A.3 Development is permitted by Class A subject to the following conditions—
(a)the materials used in any exterior work (other than materials used in the construction of a conservatory) must be of a similar appearance to those used in the construction of the exterior of the existing dwellinghouse;
(b)any upper-floor window located in a wall or roof slope forming a side elevation of the dwellinghouse must be—
(i)obscure-glazed, and
(ii)non-opening unless the parts of the window which can be opened are more than 1.7 metres above the floor of the room in which the window is installed; and
(c)where the enlarged part of the dwellinghouse has more than a single storey, or forms an upper storey on an existing enlargement of the original dwellinghouse, the roof pitch of the enlarged part must, so far as practicable, be the same as the roof pitch of the original dwellinghouse.
A.4—(1) The following conditions apply to development permitted by Class A which exceeds the limits in paragraph A.1(f) but is allowed by paragraph A.1(g).
(2) Before beginning the development the developer must provide the following information to the local planning authority—
(a)a written description of the proposed development including—
(i)how far the enlarged part of the dwellinghouse extends beyond the rear wall of the original dwellinghouse;
(ii)the maximum height of the enlarged part of the dwellinghouse; and
(iii)the height of the eaves of the enlarged part of the dwellinghouse;
(iv)where the enlarged part will be joined to an existing enlargement of the dwellinghouse, the information in sub-paragraphs (i) to (iii) must be provided in respect of the total enlargement (being the enlarged part together with the existing enlargement to which it will be joined);
(b)a plan indicating the site and showing the proposed development and any existing enlargement of the original dwellinghouse to which the enlarged part will be joined;
(c)the addresses of any adjoining premises;
(d)the developer's contact address; and
(e)the developer's email address if the developer is content to receive communications electronically,
together with any fee required to be paid.
(3) The local planning authority may refuse an application where, in the opinion of the authority—
(a)the proposed development does not comply with, or
(b)the developer has provided insufficient information to enable the authority to establish whether the proposed development complies with,
the conditions, limitations or restrictions applicable to development permitted by Class A which exceeds the limits in paragraph A.1(f) but is allowed by paragraph A.1(g).
(4) Sub-paragraphs (5) to (7) and (9) do not apply where a local planning authority refuses an application under sub-paragraph (3) and for the purposes of section 78 (appeals) of the Act such a refusal is to be treated as a refusal of an application for approval.
(5) The local planning authority must notify each adjoining owner or occupier about the proposed development by serving on them a notice which—
(a)describes the development by setting out the information provided to the authority by the developer under paragraph A.4(2)(a);
(b)provides the address of the proposed development;
(c)specifies the date when the information referred to in sub-paragraph (2) was received by the local planning authority and the date when the period referred to in sub-paragraph (10)(c) would expire; and
(d)specifies the date (being not less than 21 days from the date of the notice) by which representations are to be received by the local planning authority.
(6) The local planning authority must send a copy of the notice referred to in sub-paragraph (5) to the developer.
(7) Where any owner or occupier of any adjoining premises objects to the proposed development, the prior approval of the local planning authority is required as to the impact of the proposed development on the amenity of any adjoining premises.
(8) The local planning authority may require the developer to submit such further information regarding the proposed development as the authority may reasonably require in order to determine the application.
(9) The local planning authority must, when considering the impact referred to in sub-paragraph (7)—
(a)take into account any representations made as a result of the notice given under sub-paragraph (5); and
(b)consider the amenity of all adjoining premises, not just adjoining premises which are the subject of representations.
(10) The development must not begin before the occurrence of one of the following—
(a)the receipt by the developer from the local planning authority of a written notice that their prior approval is not required;
(b)the receipt by the developer from the local planning authority of a written notice giving their prior approval; or
(c)the expiry of 42 days following the date on which the information referred to in sub-paragraph (2) was received by the local planning authority without the local planning authority notifying the developer as to whether prior approval is given or refused.
(11) The development must be carried out—
(a)where prior approval is required, in accordance with the details approved by the local planning authority;
(b)where prior approval is not required, or where sub-paragraph (10)(c) applies, in accordance with the information provided under sub-paragraph (2),
unless the local planning authority and the developer agree otherwise in writing.
(12) The local planning authority may grant prior approval unconditionally or subject to conditions reasonably related to the impact of the proposed development on the amenity of any adjoining premises.
(16) When computing the number of days in sub-paragraph (5)(d), any day which is a public holiday must be disregarded.
Explore GPDO Part 1
Choose the work you are planning. These guides explain the English rules for houses.
- Part 1 overview
Start here for permitted development at a house - Class A: house extension and alteration
Rear and side extensions, windows and doors - Class AA: additional storeys
Build upwards above an existing house - Class B: roof enlargement
Dormers and hip-to-gable enlargements - Class C: other roof alteration
Rooflights and other roof alterations - Class D: porch
Porches outside an external door - Class E: outbuilding
Garden buildings, pools and other incidental development - Class F: hard surface
Driveways, paths and patios - Class G: chimney and flue
Chimneys, flues and soil and vent pipes - Class H: satellite dish
Microwave antennas on the house or in its curtilage - Paragraph I: definitions
Terms used in Part 1
Page Updated: 25th September 2026